Seeking relief from hot days and hotter nights?
You know the big blue sign in Kittery that greets drivers coming up the highway? It reads without a trace of irony: “Maine: the way life should be.” I’ve heard plenty of grumbling asides over the years about how off that line is – five months of winter and black-fly season are usually mentioned as often taxes and summer road construction. It’s hard to dispute, though, just how pleasant a bright summer day in Maine can be, especially when the air is crisp and dry. Weeks of cold and snow fade into memory as warmth you’d almost given up on suffuses through you.
If only it ended there. Warm weather can be a boon for our personal comfort by day, but it creates discomfort by night. You’re ready for slumber, but that attic above you has been warming up all day. The sauna you never wanted in your home is just a few feet above your head, and every summer night you feel it.
Add humidity to the scenario described above and your night will certainly be less than restful. No wonder so many of us rush to the store and snap up the air conditioners and window fans at the first sign of humid tropical air coming up from the south. No wonder our electrical bills spike in the summer months. No wonder we sometimes lie awake at night, feverishly pining for autumn’s return.
Life doesn’t have to be this way, even in Maine. Maybe you’ve considered rolling out some more pink stuff in the attic; no one can blame you for thinking that will solve all of your problems, though it won’t help as much as you thought it would. The truth is, you have two, perhaps even three, problems, and insulation will only solve one of them.
The first, and smaller, problem is radiant heat. Suffice it to say that sunlight does indeed warm up your house. Daytime temperatures on your roof deck alone can exceed 140ºF, especially if your shingles are dark. At night, when temperatures usually drop, that absorbed heat is released. If your attic insulation is ineffective, you’ve got a giant low-grade radiator hanging over your head, providing you with all the heat you never wanted in the summertime. If you live in a Cape-style home, chances are your sloping sidewalls and knee-wall attics are also uninsulated, which provides a few more radiant surfaces for your enjoyment.
As I mentioned, there are two, possibly three, problems at work here, and the second – airflow - is trickier. The old adage says that heat rises, but the truth is that heat will flow anywhere it’s enticed to go by a difference in air pressure. In winter, cold air (which is denser) wants to push in through tiny leaks and cracks in the lower parts of your heated home, which drives the warm air up and out through similar holes and seams in the upper sections of your house. In the summer, this “stack effect” reverses: cool air in your home seeks to get outside through leaks in the basement and rim joists, which pulls that hot attic air inside any way it can - through cracks in the ceiling, ventilated recessed lights, even the joints in your attic where wall studs and beams meet sheetrock or plaster. These little highways of hot air are delivering carloads of unwanted visitors to the inside of your home, and they’re dancing on that hot ceiling you’re staring at.
The solution to this problem is relatively simple to describe, but painstaking to effect in reality. Stopping the stack effect involves sealing the surfaces wherever those little highways (building science geeks call them ‘chases’) are found. The vast majority are in your attic and basement. Whether you’re using expanding foam, mastic or caulking, blocking those chases is essential if you’re going to keep the unwanted air, cold or hot, out of your living space.
Remember earlier when I mentioned the futility of just laying down another layer of fiberglass batts? You need an insulation material that retards the flow of air, and unfortunately, fiberglass batts are more akin to their cigarette filter cousins than most of us would like to admit. A better alternative is blown-in cellulose, which will reinforce the air sealing of chases to ‘cap’ the attic above your living space. In contrast to the pink stuff, cellulose is 100% recycled (very often you can see the letters still on the tiny squares of newsprint in it), non-toxic, and insect-repellent, thanks to the addition of boric acid. Packed densely into the sloping sidewalls on a Cape, it does of great job of keeping the upstairs cooler in the summer and warmer in the winter.
After air sealing and attic insulation, the last big thing we may need to address is attic ventilation. Fog and marine weather make ventilation tricky in Maine, but the general rule can be summed up in one ratio: one square foot of ventilation for every three hundred feet of attic space. With so many different types of vents in common use (ridge, gable, soffit and roof), it’s not uncommon to find an over-ventilated roof. Optimizing your attic’s ventilation can help the insulation up there perform at its best, and can even help your roof deck last longer.
Summer doesn’t have to mean choosing between sweltering nights or the glacial cool of an air conditioner eating a hole in your family’s budget. Life in Maine can live up to its billing on the highway sign, but there’s often a bit of work involved. If we get the air sealing, insulation and attic ventilation done right, there’s no reason we can’t all sleep better through the summer months, enjoying the pleasures of the season instead of dreaming of the return of cooler weather.
By Cree Hale Krull, Energy auditor based in Bath with Evergreen Home Performance in Rockland Maine. He can be contacted by email at firstname.lastname@example.org